Adaptation and Natural Selection
1
2
Adaptations
A. Types of adaptation
i.
structural adaptations
a. camouflage
1. warning coloration
2. mimicry
ii.
physiological adaptations
Types of Natural Selection
A. Directional Selection
B. Stabilizing Selection
C. Disruptive Selection
Adaptations:
??What is an adaptation??
A trait that helps in survival
Structural adaptation – adaptations that involve the body of the
organism. IE. Wings, fins, webbed feet, etc.
Structural adaptations continued…
Camouflage – helps organism blend into the environment
Warning coloration – the color of the organism is an indicator to
a predator that it does not taste good
Mimicry – one organism looks like another that is harmful
Physiological adaptation – adaptations that involve the
metabolism (life processes) of the organism. IE. Webs, venom,
etc.
Types of Natural Selection
According to the modern theory of evolution, natural selection
disturbs genetic equilibrium. As a result, the allele frequency in
the population will change. In this way, natural selection
determines which adaptations are favorable for a species. There
are three main types of natural selection.
Directional Selection – an extreme phenotype becomes a
favorable adaptation. The environment favors the extreme
phenotype causing the population to evolve.
Stabilizing Selection – the average phenotype is favorable and
the extreme phenotypes are unfavorable. The extremes die off.
Disruptive Selection – the average phenotype is not favorable and
the two extremes become favorable. This type is very rare.
Speciation and Observed Natural Selection
1
Speciation
A Geographic Range
I range
B Types of Speciation
I isolation
II geographic isolation
III reproductive isolation
IV polyploidy
V adaptive radiation
C Convergent Evolution
2
D Coevolution
Observed Natural Selection
A Industrial melanism
I peppered moths
B Bacterial Resistance
I antibiotics
C Insect Resistance to DDT
I mosquitos
??What is speciation??
The creation of a new species - accumulated adaptations
Each species is found in a particular region of the earth.
This region is called a range.
range_ - the area in which a given species is found.
??Do you think individuals within a population that are at
opposite ends of a range will be similar or different?? Why?
Different due to different environments!!
Types of speciation
Anything that prevents two groups within a species from
interbreeding is called isolation. Through mutation, genetic
recombination, and natural selection, a different gene pool
will evolve in each group.
_isolation_ - something that prevents two groups in the
same species from breeding.
1
– geographic isolation - happens when a population is divided
by a natural barrier. IE mountain, desert, river, etc.
??Over time, what will be the result of geographic isolation?? Why??
Speciation due to accumulated adaptations
2
- When groups have been separated for a long time, they
lose the ability to breed with each other. This is called
reproductive isolation
Geographic isolation will eventually cause reproductive isolation!!!
3
- Speciation- Speciation can occur suddenly when abnormal
meiosis or mitosis results in polyploidy (unusual number of
chromosomes). When the offspring can interbreed only
among themselves, they are considered a new species.
Types of speciation continued…
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adaptive radiation - when one species evolves into a number
of different species, each occupying a new environment. IE
Darwin’s finches
Convergent Evolution
As a result of geographic isolation, organisms that are not closely
related may develop similar adaptations and come to resemble
each other. Natural selection that causes unrelated species to
resemble one another is called convergent evolution. Convergent
Evolution produces analagous structures. IE bird wings and insect
wings.
Analogous structures and convergent evolution - organisms that
are not closely related, but develop similar adaptations due to
natural selection.
Coevolution
Two or more species can evolve in response to each other through
cooperative or competitive adaptations. This is called
coevolution. Coevolution reduces competition between species
and benefits both species. IE Birds/flowers –gazelles and
cheetahs
Coevolution - when two species evolve together
Genetics and Evolution
I.
Genetics and Evolution
A. Population Genetics
i. Populations
ii. Population genetics
iii. Gene pool
iv. Evolution
B. Genetic Sources of Variation
i. Mutations
ii. Genetic recombination
iii. Migration
iv. Genetic drift
?What is a population?
A group of potentially interbreeding individuals – one species in
an area
?Does evolution happen to individuals or populations?
Population Genetics:
Evolution – a change in allele frequency within a population over
time.
!!!Even though evolution happens to
populations, individuals are the units of
natural selection!!!
Population – a group of organisms of the same species living
together in a given region and capable of interbreeding.
Population Genetics – the study of the changes in genetic makeup
of populations.
IE. All of the individuals in a population may have one type of allele (versions
of a gene). There may be only one individual with a type of mutation.
Probabilities, Percentages, Statistics, and Odds
Gene pool – the total of all the alleles present in a population
Read the definition of evolution on the front page. Does
the gene pool ever change??
Genetic sources of variation:
Mutations: - Mutations are very rare and are usually harmful to
the individual. If the mutation is beneficial, there is a good
chance that natural selection will promote the resulting trait.
Genetic recombination – new combinations of alleles are produced
during crossing-over and independent assortment.
MEIOSIS!
?What does it mean to migrate?
Migration – when individuals move into or out of a population,
alleles are brought in or out of that population. Migration affects
small populations the most.
Genetic drift – a change in the gene pool of a small population
that is brought about by chance. IE. An endangered plant species
has only 80 individuals. If only three of these individuals have a
certain allele, and they die, the gene pool is reduced.
Questions:
1
Name the sources of variation within a species according to the
modern theory of evolution.
2
What is a population?
3
Define the term “gene pool” in your own words.
Name:_______________
Homework Directions: Using the internet and your textbook for
help, discuss the 7 terms listed below. Two descriptive sentences
for each term is enough. Be sure to think of genetics and
evolution as you work.
-population
-population genetics
-gene pool
-mutations
-genetic recombination
-migration
-genetic drift
Name:______________
Do now Directions:
PART A:
Stabilizing Selection
Directional Selection
Original population
Disruptive Selection
-In part A, match up the term with the graph
-For part B, use the internet to give an example of
each of the structural adaptations listed below.
PART B:
-camouflage –
-warning coloration –
-mimicry –
Name:_________________
Animal Adaptations Webquest
http://www.esc9.net/webquests/Science%202/Mary%20Ewing/animaladaptationl.html.html
Directions: - Using the link above, you will find a webquest about animal adaptations.
Once there, you will be able to use the links to answer the questions below. DO NOT
print out the “Animal Adaptation Sheet”!! This will be the only handout you will need.
1. List at least 5 different kinds of bird beaks classified according to the different
jobs that they perform. Give an example of a bird that has each type of beak.
Type of beak
1. ___________________
2. ___________________
3. ___________________
4. ___________________
5. ___________________
Name of bird
_________________
_________________
_________________
_________________
__________________
2. A. How do birds’ feet help them to survive in their different environments?
B. Give 5 examples of how feet are designed for different jobs.
1.__________________________________________
2. __________________________________________
3. __________________________________________
4. __________________________________________
5. __________________________________________
3. A. What is mimicry?
B. How does it benefit the animal?
4.
How is camouflage different from mimicry
When you are done, design and draw a picture of an imaginary animal with it’s
own unique adaptations. Tell how the adaptations help that animal live in it’s
imaginary environment. Feel free to do this on the back of this sheet.